1. Field of the Invention
The present invention relates to an apparatus for separation and recovery of an olefin from a mixture of a paraffin and an olefin in the petroleum refining industries, petrochemical industries and the like, and a method therefor.
2. Background Art
An olefin, which is represented by ethylene and propylene, is a basic chemical material produced in the petroleum refining industries, petrochemical industries and the like, and in the production process and the utilization process thereof, an olefin is necessarily separated and recovered from a mixture of a paraffin and an olefin.
The separation of an olefin from an olefin-paraffin mixture is currently performed by distillation in general. However, due to the boiling points of an olefin and a paraffin, which are very close to each other, considerable energy is consumed in the separation by distillation, and a large-scale distillation tower having a large number of steps of from 120 to 180 is necessarily used.
Accordingly, considerable energy saving and simplification of the process may be realized by enabling highly selective permeation separation of an olefin from an olefin-paraffin mixture with a separation membrane.
U.S. Pat. Nos. 5,670,051, 5,769,927, 5,785,739, 6,361,582 B1, 6,414,202 B1, 6,428,606 B1, 6,525,236 B1 and 7,479,227 B1 propose enhancement of efficiency of the separation and recovery process of an olefin through membrane separation by Membrane Technology and Research, Inc.
These membrane processes are generally performed under high pressure, and therefore, the ordinary polymer membrane undergoes plasticization and loses the permeance and the separation selectivity. JP-T-2006-508176 proposes the use of a polyimide membrane that has good durability against plasticization, but the membrane has an extremely small permeance to an olefin.
Journal of Membrane Science, vol. 184, pp. 209-219 (2001) and Industrial & Engineering Chemistry Research, vol. 44, pp. 226-230 (2005) propose the use of crystalline porous aluminosilicate excellent in durability, such as zeolite, as a material for a separation membrane. However, it is the current situation that the separation membranes having been proposed have a very small permeance to an olefin. The smaller olefin permeance causes the necessity of a larger membrane area, which brings about increase of the cost of the equipments for membrane separation. Accordingly, the too small olefin permeance may lead difficulty in economy, and thus it is difficult to use the membranes in industry. For example, the zeolite membranes disclosed in the aforementioned two literatures have a propylene permeance of less than 100 GPU, but a ceramic film that can be industrially used necessarily has a propylene permeance of 300 GPU or more in consideration of economy. With respect to the unit of permeance, 1 GPU is equal to 10−8 cm3 (STP: standard temperature and pressure)/(s·cm·cmHg) and 3.36×10−10 mol/(m2·s·Pa).
Journal of Membrane Science, vol. 311, pp. 326-335 (2008) reports the propylene-propane permeation separation factor of a separation membrane formed of crystalline porous titanosilicate. The membrane exhibits relatively good initial capability, i.e., a propylene permeance of 235 GPU and a separation factor (propylene/propane) of 5.5, but the literature reports that the permeation separation factor is largely deteriorated during the test for 15 days.